1. Field of the Invention
The present invention relates to an automatic control type electrical air cleaner or dust collector.
2. Description of the Prior Art
A typcially conventional electrostatic precipitator is disclosed in U.S. Pat. No. 3,740,927, which comprises as shown in FIG. 1 a first section 20 having a plurality of negatively charged vertical wires W arranged between at least one or more pairs of positively charged vertical plates P1-P3 a second section 30 having a plurality of metallic girds G21 to G26 attached to the respective vertical plates in the first section 20. A corona discharge may be developed between the positively charged plates P1-P3 and the negatively charged W. The second section 30 abuts the end of the first section 20 and the grids G21-G26 thereof are parallel to each other. The first and last grids G21 and G2l are connected to a voltage source so as to prevent a corona discharge, and the remaining grids G22 to G25 are "floated" between the grids G21 and G26 so as to be charged by voltage induced toward the grids.
With this structure, particles of matter entering the second section 30 and traversing the openings of the respective grids will respond to the electric field between adjacent grids and to produce an aerodynamic flow pattern between the grids. As a result. there is an advantage that dust may be collected and removed from fluid medium, but there are problems in that the electrostatic precipitator is complicated and the manufacturing cost is expensive, and since the metallic grids are in a "floating state", the dust collecting efficiency is decreased.
Another conventional electrical dust collector, as shown in FIGS. 2(a), 2(b) and 2(c), includes a discharging electrode unit 3A having a plurality of sharp-edged projections defining electrodes 3 for forming local electric field 3, a dust collecting electrode unit 2A having dust collecting electodes for collecting the dust particles positively ionized by the discharging electrodes 3, and insulating supports 1 for maintaining a constant distance between the discharging electrodes and dust collecting electrodes to insulate therebetween. When the power voltage (not shown) is supplied to the dust collector under a condition that the electrode units 2A and 3A are fixed to the insulating supports 1, the discharging electrodes 3 are positively charged with electricity, while the dust collecting electrodes 2 are negatively charged, whereby an ionized field is formed between the discharging electrodes 3 and the dust collecting electrodes 2. As a result, if the air is introduced in the dust collector and passed through the ionized field, dust particles entrained in the air are ionized and charged positively and thus the positively charged dust particles are conducted by and collected onto the dust collecting electrodes. In this way, the dust collector performs a given air cleaning function.
With the construction as mentioned above, however, the dust collecting efficiency of the dust collecting electrodes 2 is largely variable on the basis of distance separating the dust collecting electrodes from the discharging electrodes, collecting voltage, temperature and humidity of the interior and exterior of the dust collector, speed of the air flow and amount of dust particles built-up on the dust collecting electrodes.
More particularly, since the electrical dust collector operation generally is classified into three selective air flow speeds, namely, high, medium and weak, the intensity of the air flow may change. And, since the temperature and humidity can vary during the year, it is necessary to be able to control the efficiency of the dust collecting electrodes.
In the conventional electrical dust collector, the collecting voltage for controlling the collecting efficiency cabn not be varied, and a distance separating the dust collecting electrodes from the discharging electrodes can not be effectively adjusted to vary the collecting efficiency. Accordingly, there are problems in that unexpected variation of the collecting efficiency due to the aforementioned factors can not be avoided.